I. Field of the Invention
The present invention relates to methods and systems for the removal and replacement of bridge sections.
II. Description of Present Methods and Systems
At the present time one method and system used for the removal and replacement of railway bridges is called the "roll-in" method. Most railroad bridges have at least two parallel railroad tracks whose railway beds may be located on a single bridge structure.
In the "roll-in" method the first step in demolishing and replacing such a railroad bridge is to clear the site area around the bridge so that construction equipment, such as cranes, may be brought near the bridge. Frequently this is an involved, complicated and costly procedure since many railroad bridges are erected over busy highways and in congested areas. For example, many months of preparation may be required to clear the area around a railroad bridge in order to utilize a heavy-duty crane. Such preparation may involve obtaining permits, coordination among construction crews and various utility crews to relocate power, telephone and other overhead utility lines and the closing of one or more lanes of the highway for a number of weeks. Sometimes permission must be obtained to bring the equipment across, or onto, private land. Sometimes temporary haul roads must be built and the land later restored. Sometimes gravel or other suitable material must be spread on the site to provide a foundation for heavy equipment. In addition, sometimes special covers are required for underground utility lines. In addition, the highway traffic may be detoured, which may cause congestion on adjacent highways. Once the area has been cleared, a heavy-duty crane may be brought in and utilized on the site. A heavy steel temporary structure is then constructed to form a platform (ways) along the highway.
In the "roll-in" method the new bridge section is then constructed on top of the ways parallel to the existing structure. Traffic below must be stopped each time a heavy member is erected.
After the construction of the new section is complete, the old section may be removed by sliding it sidewise along the ways. This section must then be demolished over the highway below, resulting in further interference and delays.
When the old section has been disposed of, the new replacement section may be slid sidewise into position.
After all construction is complete, the ways must be dismantled and removed and the entire construction site restored.
The "roll-in" method may not be practicable with some bridges, for example, water crossings, and in those situations heavy-duty marine equipment may have to be used for the bridge's removal and replacement and such marine equipment may require preliminary dredging.
An improvement in a system to build bridges is described in U.S. Pat. No. 3,902,212 entitled "Building of Multispan Bridges Or The Like Works By The Cantilever Method."